1. Field of the Invention
This invention relates generally to grinding fixtures, and more particularly to a grinding fixture capable of selectively moving a workpiece forward and rearward relative to a grinding wheel while simultaneously rotating it eccentrically, and of rotating the workpiece concentrically to grind predetermined angular and curved surfaces.
2. Brief Description of the Prior Art
The grinding or re-working of drill bits, taps, reamers, etc., requires accurate and uniform grinding of the multiple angular and curved surfaces. Some tools, such as reamers, are fluted to define wings, and require exceedingly careful treatment to avoid accidental grinding of adjacent surfaces while producing a proper conical reaming configuration and clearance behind the leading edge of each wing portion. There are several patents disclosing grinding fixtures which have been designed to produce various angular and curved surfaces on drill bits, taps, reamers, etc.
Wilson, U.S. Pat. No. 2,672,714 discloses a fixture having a V-block and a cylindrical barrel resting in the V-block and having a flange at one end to engage the end of the V-block. The barrel is rotated while in tangential contact with the V-surfaces and has an eccentric bore. A tool holding sleeve is slidably and rotatably mounted in the eccentric bore and has a flange at one end. The barrel flange has a series of circumferentially spaced indexing holes and the sleeve flange is provided with an indexing pin which will engage selective ones of the indexing holes. The sleeve may be withdrawn partially from the barrel, rotated, and returned to a plurality of angular positions.
Detrow, U.S. Pat. No. 2,700,854 discloses tap grinding fixture having a support base with a vertically extending bracket revolvably mounted thereon and which terminates in a circular head. Another bracket having a coacting circular head is revolvably connected to the first circular head and has a forwardly extending portion disposed off center from the circular head and terminating in a ring member. A cylindrical body structure having an end flange is adjustably secured to the ring member. The body structure has a longitudinally extending bore therethrough with a cylindrical tube assembly mounted in the bore. The cylindrical tube assembly includes a pair of coacting inner and outer eccentric sleeves adjustable one with respect to another. A chuck spindle is carried by the inner sleeve and projects beyond opposite ends of the sleeves. An actuating disc is mounted on the outer sleeve adjacent the end of the body structure and an indexing plate is mounted on the spindle adjacent the actuating disc. An actuating lever extends outwardly from the actuating disc for controlling the movement of the chuck spindle in an orbital path. A number of indexing plates must be installed for various different taps according to the number of their flutes.
Studler, U.S. Pat. No. 2,797,538 discloses a grinding tool having a fixed casing with a spindle received in a bore in the casing. The spindle has a chuck at the forward end and a bushing is disposed at the rear of the casing bore to guide the spindle. The rear end of the spindle extends beyond the bushing. The spindle has a cam face on its forward side toward the bushing. A double faced cam collar is mounted on the spindle and cooperates with a cam follower arm carrying a ball. When the spindle rotates continuously in one direction, the cam faces ride up on the ball to move the tool toward and against the grinding wheel under spring pressure.
Farnsworth, U.S. Pat. No. 3,090,633 discloses an index mechanism for a chuck having a housing and a spindle assembly rotatably mounted in the housing which grips the workpiece for rotation therewith. The indexing mechanism comprises a cylindrical member secured to the spindle assembly and a series of balls fixed circumferentially around the cylindrical member with adjacent balls abutting against one another to form a V-shaped space between each pair of balls. A plunger shiftably mounted on the housing has a portion insertable into the space between the balls to prevent rotation of the spindle assembly relative to the housing.
Zapart, U.S. Pat. No. 4,100,702 discloses an indexing fixture comprising a generally rectangular rigid upstanding housing having a longitudinal bore. A fixed cylindrical hollow tubular member is secured in the bore and has a rear flange engaging the rearward wall of the housing. A hollow tubular spindle is slip fitted in the fixed tubular member and has a front flange positioned forwardly of the housing front wall. A toothed indexing wheel is secured to the rearward portion of the spindle. A collet-receiving manipulating ring is loosely keyed to the indexing wheel and rotates freely thereon. A rotatable indexer member extends down through the top of the housing to be moved into the rotary path of the indexing wheel. A detent is disposed adjacent the front flange to be moved into engagement with a dog mounted on the front flange.
Bernard et al, U.S. Pat. No. 4,485,596 discloses a drill chuck supporting cradle which is mounted for limited rotation on a tiltable cross feed table. The cradle is provided with a band or bridge affixed at one side of the cradle and attached at the other side by an eccentric so that the band can be tightened to hold a chuck in fixed relation to the cradle. The cross feed table is supported by a standard which has a pair of stop pins which limit the pivotal movement of the table.
Zapart, U.S. Pat. No. 3,887,202 discloses a grinding fixture which has a rotatable workpiece-holding spindle which may be indexed at any selected angular division of a circle. The device utilizes at least two circumferentially spaced indexers radially insertable into and retractable from interspaces between adjacent teeth spaced at ten degree intervals around the circumferential face of an associated rotatable spindle.
The present invention is distinguished over the prior art in general, and these patents in particular by a fixture for holding and positioning reamers and other objects for grinding which has a support base connectable to a flat horizontal surface and its upper portion is positioned at an angle relative to the horizontal surface. A cylindrical sleeve rotatably mounted on the upper portion of the support base has an eccentric longitudinal bore and a radial flange at its rearward end. A cylindrical spindle rotatably received within the eccentric bore has a mounting flange at its forward end to receive a chuck for holding an object to be ground and a rear flange adjacent the sleeve radial flange. A handle extending from the sleeve rotates the sleeve about its longitudinal axis. An axial guide flange between the support base and sleeve moves the sleeve forward or rearward upon rotation of the sleeve. A retractable rod connected between the spindle flange and sleeve flange selectively locks the spindle and sleeve together for rotation as a unit about the longitudinal sleeve axis or releases the spindle for rotating only the spindle about its longitudinal axis relative to the sleeve.
The spindle rotates partially about the centerline of the sleeve when locked with the sleeve whereby the object being ground is eccentrically rotated in a radial spiral motion when the handle is pivoted. When the axial guide flange is angularly positioned the object being ground moves simultaneously forward or rearward and in a radial spiral motion. When the spindle and sleeve are unlocked the object being ground may be rotated only about its own longitudinal axis and positioned to grind subsequent surfaces.